feat: add pricing checkout flow, MFA type fixes, and Wave 13 audit docs

- Pricing page: enhanced with checkout modal integration, plan
  comparison table, and subscription funnel
- Payment return page: new VNPay/MoMo callback handler
- Subscription components: new checkout-modal with payment method
  selection (VNPay, MoMo, ZaloPay)
- API modules: type-safe PII encryption, improved error handling in
  MFA/auth/payments/analytics/search/notifications modules
- Audit docs: comprehensive Wave 13 platform assessment, pricing
  audit, production readiness checklist
- Updated PROJECT_TRACKER with Wave 13 status

Co-Authored-By: Paperclip <noreply@paperclip.ing>

CHANGELOG.md

@@ -7,6 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added (CEO Audit Wave 13 — 2026-04-12)
+- CEO audit routine (TEC-1915) — full codebase audit + project state review
+- Plan document with 7-section report: audit summary, critical issues, priorities, recommendations
+- 6 new subtasks created (TEC-1918 through TEC-1923) for Wave 13
+- Updated PROJECT_TRACKER with Wave 13 tracking section
+
+### QA Results (2026-04-12)
+- Lint: PASS (0 errors)
+- TypeScript: 7 errors in web test files (vitest types missing) — TEC-1918
+- Unit Tests: 232 files, 1454 tests, ALL PASS
+- Build: ALL 3 packages build successfully
+- Git: Clean working tree
+
 ### Added
 - CEO full audit & implementation plan (TEC-1882) — 8-part report covering architecture, quality, security
 - 7 new subtasks created (TEC-1888 through TEC-1894) for Wave 11D-13